In the manufacture of semiconductor components or liquid-crystal components, a sputtering apparatus is used to form various kinds of wiring and electrodes. For example, various kinds of metal thin films and intermetallic compound thin films are formed on a film-formation substrate such as a semiconductor substrate and a glass substrate by a sputtering method. The aforesaid thin films are used as, for example, a wiring layer, an electrode layer, a barrier layer, a foundation layer (a liner material), and the like. Impurities in the thin films have an adverse effect on operation reliability of semiconductor devices. For this reason, a high purity of 4 N or more is required of sputtering targets used for forming the thin films.
Metal materials used as sputtering targets are manufactured by, for example, a sintering method or a melting method. In the manufacture of the above metal materials, their raw materials are refined for reducing impurities. An ingot is formed from the above material whose impurities are reduced. The ingot is worked by forging, rolling, and so on to be formed into a billet. The billet is heat-treated for its structure control and so on. The billet is further shaped to a predetermined size by machining and the resultant billet is bonded to a cooling backing plate as required, and as a result, it is possible to manufacture the sputtering target.
As wafers and the like become larger, larger sputtering targets are required. In conventional methods of manufacturing sputtering targets, the increase of the target size inevitably increases manufacturing cost.